Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber devices.’ At least one other terminal, e.g. used in conjunction with subscriber devices, may be a fixed terminal, e.g. a base station, repeater, and/or access point. Such a RAN typically includes a system infrastructure that generally includes a network of various fixed terminals, which are in direct radio communication with the subscriber devices. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve subscriber devices in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber devices that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber device within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another and may be non-overlapping or partially or fully overlapping with one another.
RANs may operate according to an industry standard land mobile radio (LMR) protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), the TETRA standard defined by the European Telecommunication Standards Institute (ETSI), the Digital Private Mobile Radio (dPMR) standard also defined by the ETSI, or the Digital Mobile Radio (DMR) standard also defined by the ETSI, or may operate according to other radio protocols such as Long Term Evolution (LTE) or Third Generation (3G) (3GGP or 3GGP2).
Communications in accordance with any one or more of these protocols or standards, or other protocols or standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols. Subscriber devices in RANs such as those set forth above send and receive auditory data (encoded voice, audio, or audio portions of an audio/video stream) and other types of data in accordance with the designated protocol.
Various LMR systems may operate in either a conventional or trunked configuration. In either configuration, a plurality of subscriber devices are partitioned into separate groups of subscriber devices (e.g., talkgroups) for group-based distribution of audio and/or other data.
In a conventional system, each subscriber device in a group is selected to a particular frequency for communications associated with that subscriber device's group. Thus, each group is served by one channel, and multiple groups may share the same single frequency (in which case, in some embodiments, group IDs may be present in the group data to distinguish between groups using the same shared frequency).
In contrast, a trunked radio system and its subscriber devices use a pool of traffic channels to support virtually an unlimited number of groups of subscriber devices. Thus, all groups are served by all channels. The trunked radio system works to take advantage of the probability that not all groups need a traffic channel for communication at the same time. When a member of a group requests a call on a control or rest channel on which all of the subscriber devices in the system idle awaiting new call notifications, in one embodiment, a call controller assigns a separate traffic channel for the requested group call, and all available members assigned to or subscribed to the group move from the assigned control or rest channel to the assigned traffic channel for the group call. In another embodiment, when a member of a group requests a call on a control or rest channel, the call controller may convert the control or rest channel on which the subscriber devices were idling to a traffic channel for the call, and instruct all subscriber devices that are not participating in the new call to move to a newly assigned control or rest channel selected from the pool of available channels. With a given number of channels, a much greater number of groups can be accommodated in a trunked system as compared with conventional radio systems.
Group calls may be made between wireless and/or wireline participants in accordance with any particular LMR protocol. Associated and/or subscribed group members for group calls may be statically or dynamically defined. That is, in a first example, a user or administrator working on behalf of the user may indicate to the radio network (perhaps at a call controller, radio controller, zone controller, site controller, or other network device) a list of members of a group at the time of the call or in advance of the call. The group members (e.g., subscriber devices) could be provisioned in the network by the user or an agent, and then provided some form of group identity or identifier, for example. Then, at a future time, an originating user of a subscriber device in a group may cause some signaling to be transmitted indicating that he or she wishes to establish a communication session (e.g., group call) with each of the pre-designated participants in the defined group.
In another example, subscriber devices may dynamically affiliate with a group (and also disassociate with the group) perhaps based on user input, and the switching and/or radio network may track group membership and route new group calls according to the current group membership. Group membership information may be shared with dispatchers via dispatch consoles and/or with certain privileged subscriber devices such as those used by commanders or other qualified users.
One problem that has arisen with the increasing proliferation of group-based wireless subscriber devices is that in the event of a catastrophic event or in anticipation of a pending or likely catastrophic event, a commander, dispatcher, or other user in the radio network may desire to issue an emergency notification to a particular group that requires acknowledgment by each of the subscriber devices of that particular group. For example, an evacuation order may be issued to a firefighter group in response to a partial roof collapse or in anticipation of an expected full or partial roof collapse, and the person or device initiating the evacuation order may like to ensure that every member of the group has received the evacuation order.
However, in RANs in general, and in trunked RANs in particular, where radios may be on a control channel, voice traffic channel, data traffic channel, or otherwise scanning other known channels, it is difficult to reach all members of a particular group and/or confirm receipt of the emergency notification by each member of the particular group. Furthermore, once all members of the particular group have been reached with a request to acknowledge the emergency notification, interference and collisions are likely to occur as all members of the particular group attempt to acknowledge the particular message at substantially a same time. Such issues and occurrences could delay or prevent an initiator of an emergency notification in a trunked RAN from reliably transmitting such emergency notifications to all members of the particular group and reliably receiving acknowledgments indicating whether such notifications had been received by all members of the particular group.
Accordingly, what is needed is an improved method and apparatus for managing group-based emergency notifications and acknowledgments in a trunked RAN.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.